Photonic switches, such as Mach-Zehnder Interferometer (MZI) switches allow for the controllable routing of optical signals. Ongoing efforts are being made to design photonic integrated circuits (PICs) which incorporate potentially large numbers of such switches.
Switches based on the MZI architecture require correctly tuned control signals in order to operate with an adequately high extinction ratio. The MZI switch uses phase shifters to manipulate input optical signals. For example, a 2×2 MZI switch is operable in a cross configuration (in which first and second input signals are routed respectively to second and first outputs) and a bar configuration (in which first and second input signals are instead routed respectively to the first and second outputs). The control signal applied to the phase shifters determines whether the cross or bar configuration, or an intermediate mixture between the two configurations, is achieved.
However, factors such as manufacturing variability and environmental conditions can cause operating difficulties for a photonic switch such as an MZI switch. In particular, it can be difficult to determine control signal levels which will provide adequately pure cross and bar signals for a given photonic switch. Although it is possible to pre-tune (and possibly periodically re-tune) switches by injecting test signals and storing the control signal levels which provide the desired level of functionality, this requires a memory to store the control signal levels, and may also require the switch to be taken offline for tuning periodically.
Therefore there is a need for a method and apparatus for monitoring and controlling a photonic switch that obviates or mitigates one or more limitations of the prior art.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.